Pulmonary oedema as judged by lung ultrasound: recent advances
Lung ultrasound remains a hot topic with the publication this year of another couple of great articles.
Tommaso Vezzosi and colleagues look at the diagnostic accuracy of lung ultrasound (LUS) for cardiogenic pulmonary oedema and correlate findings with ACVIM consensus staging system.
http://onlinelibrary.wiley.com/doi/10.1111/jvim.14692/pdf
Reassuringly they report that:
- B lines are rare or absent in @90% dogs with stage B1 and B2 heart disease
- B lines are numerous or confluent in 90% of dogs with stage C heart disease and radiographic signs of pulmonary oedema
However, they did find that a few dogs with B1 or B2 heart disease exhibited numerous B lines. It is unknown whether these dogs actually had pulmonary oedema which was not apparent on radiographs (human studies reveal that radiography may be less sensitive than LUS) or whether they had concurrent non-cardiogenic lung pathology. The jury remains out on this but we should remain alert to the possibility that some dogs without radiographic signs may have CHF.
Another snippet of usefullness is that LUS was not 100% sensitive for the presence of pulmonary oedema. A couple of dogs with stage C disease appeared to have peri-hilar oedema on radiography but had few B lines on LUS.
Personally, these findings fit very well with my experience that, overall, I can use LUS as the most convenient tool for assessing presence/absence of pulmonary oedema but, just occasionally, I meet a dog whose LUS doesn’t match what I was expecting from echocardiographic and physical findings.
Also worth mentioning that it’s possible to get asymmetrical or dorso-ventrally heterogeneous pulmonary oedema…..which complicates things a little.
In fact this is quite common:
https://www.ncbi.nlm.nih.gov/pubmed/19878003
…and is likely due to eccentricity of mitral valve regurgitant jets selectively affecting different pulmonary veins. The right lung is usually more severely oedematous in this scenario.
Vezzosi’s paper dovetails nicely with:
Accuracy of point-of-care lung ultrasonography for the diagnosis of cardiogenic pulmonary edema in dogs and cats with acute dyspnea.
https://www.ncbi.nlm.nih.gov/pubmed/28263112
…which sheds some light on the sensitivity and specificity of LUS in a real-life ‘what is wrong with my dyspnoeic patient scenario’ rather than a ‘does my DMVD dog have CHF scenario’.
More discussion to follow….must go see some patients….
